As the sun set on a second day of lockdown in Brussels, Belgian authorities asked local Twitter users to silence their accounts to keep police and military safe in their search for fugitive Paris terror suspect, Salah Abdeslam. The reaction on social media was swift and unexpected: Tweets of real-time updates and eyewitness accounts from Brussels were replaced with kittens.

"After Belgian police asked residents not to share details of the #BrusselsLockdown via social media, civilians took over the hashtag and flooded it with pictures of their feline friends," Twitter said, in summing up the way some of its community responded on its "Moments" page.

The majority of tweets appeared to not just offer a moment of levity in an extremely tense situation, the cats served a purpose, too, making it more difficult for suspected terrorists trying to gather details of the counter-terrorism operations by flooding the #BrusselsLockdown feed with memes.

In a press conference after midnight local time, authorities said they had made 16 arrests in the operation in Brussels, Reuters reports. Mr. Abdeslam, a suspect in the Paris attacks, was not among them, however, according to Belgian prosecutors, even after 19 raids.

Belgian authorities are still warning residents of possible attacks similar to those in Paris, which killed 130, fearful that Abdelsam has returned home to Brussels to perpetrate more violence.

Prime Minister Charles Michel said at the news conference that the city will remain on Belgium's fourth and highest level of security threat, meaning the threat of an attack was "serious and imminent".

"What we fear is an attack similar to the one in Paris, with several individuals who could possibly launch several attacks at the same time in multiple locations," he told a news conference.

On Monday, public transportation, schools, and shops will remain closed. NATO, which had raised its alert level since the Paris attacks of Nov. 13, said its headquarters in Brussels were open, but some staff had been asked to work from home and external visits had been cancelled.

Not since the Boston Marathon bombings in April 2013 has a major city been put on lockdown as a manhunt was underway, and a terror investigation captivated an online, international audience. In the case of Boston, Reddit users took to their accounts to leverage what amounted to a witch hunt, the threads of which were picked up by major media outlets. As Salon reports:

Innocent spectators were targeted by a scary cadre of online vigilantes and two blameless men saw their images plastered over the [New York] Post’s front page with the news that the feds were looking for them (not true). When the FBI released photos of the actual suspects, the Tsarnaev brothers, an unchastened Reddit promptly seized on the resemblance between one suspect (Dzhokhar) and a Brown University student, Sunil Tripathi, who had been missing for several weeks. Someone on Twitter claimed he’d heard Tripathi’s name on the Boston police scanner, and the story, apparently verified, spread, causing Tripathi’s family great pain. (The student’s body was later found in the Providence River.)

Two and a half years later, and with a new city shellshocked and lacking closure on a terror investigation, citizens of the EU appear to have evolved the idea of what it means to assist when so much is still unknown. Meanwhile, as the search goes on, Belgian authorities have expressed gratitude to the people of Brussels, Internet users, and those cats: